Differential recruitment of ventral pallidal e-types by behaviorally salient stimuli during Pavlovian conditioning

Abstract

Summary The ventral pallidum (VP) is interfacing striatopallidal and limbic circuits, conveying information about salience and valence crucial to adjusting behavior. However, how VP neuron populations with distinct electrophysiological properties (e-types) represent these variables is not fully understood. Therefore, we trained mice on probabilistic Pavlovian conditioning while recording the activity of VP neurons. Many VP neurons responded to punishment (54%), reward (48%), and outcome-predicting auditory stimuli (32%), increasingly differentiating distinct outcome probabilities through learning. We identified e-types based on the presence of bursts or fast rhythmic discharges and found that non-bursting, non-rhythmic neurons were the most sensitive to reward and punishment. Some neurons exhibited distinct responses of their bursts and single spikes, suggesting a multiplexed coding scheme in the VP. Finally, we demonstrate synchronously firing neuron assemblies, particularly responsive to reinforcing stimuli. These results suggest that electrophysiologically defined e-types of the VP differentially participate in transmitting reinforcement signals during learning.

Cholinergic activity reflects reward expectations and predicts behavioral responses

“… 26 , 27 However, since we hypothesized that BFCNs are sensitive to the outcome probabilities, we chose to manipulate reward probability instead, despite that this is harder to learn, as animals have to integrate over multiple trials to infer differences in probability, whereas reward size can be learned from a single trial. 28 …”

The antipsychotic drug sulpiride in the ventral pallidum paradoxically impairs learning and induces place preference

“…Recently, it has become the focus of attention, since VP demonstrates relative reward value earlier than the nucleus accumbens (NAC) 1 , and a subset of VP neurons encodes reward prediction error more robustly than the NAC 2 . Furthermore, VP neurons respond not only to reward but also to punishment and outcome-predicting stimuli 3 .…”

Training protocol for probabilistic Pavlovian conditioning in mice using an open-source head-fixed setup

“…This allows the experimenter to have full control over the outcome contingencies, making this task ideal for probing the neural mechanisms underlying the processing of probabilistic outcomes ( Pearce and Hall, 1980 ; Schultz et al., 1997 ). This Pavlovian training protocol was tested in combination with extracellular tetrode recordings ( Hegedüs et al., 2021 ) and optogenetic tagging of neurons. We confirmed that it is suitable for optogenetic manipulations and fiber photometry experiments as well.…”

“…It has been tested in combination with chronic in vivo electrophysiological recordings and optogenetic manipulations in ChAT-Cre and PV-Cre mouse lines. For complete details on the use and execution of this protocol, please refer to Hegedüs et al. (2021) .…”

“…For complete details on the use and execution of this protocol, please refer to Hegedüs et al. (2021) .…”